Installing Go from source

Introduction

Go is an open source project, distributed under a
BSD-style license.
This document explains how to check out the sources,
build them on your own machine, and run them.

Most users don't need to do this, and will instead install
from precompiled binary packages as described in
Getting Started,
a much simpler process.
If you want to help develop what goes into those precompiled
packages, though, read on.

There are two official Go compiler toolchains.
This document focuses on the gc Go
compiler and tools.
For information on how to work on gccgo, a more traditional
compiler using the GCC back end, see
Setting up and using gccgo.

The Go compilers support eight instruction sets.
There are important differences in the quality of the compilers for the different
architectures.

amd64 (also known as x86-64)

A mature implementation.

386 (x86 or x86-32)

Comparable to the amd64 port.

arm (ARM)

Supports Linux, FreeBSD, NetBSD, OpenBSD and Darwin binaries. Less widely used than the other ports.

arm64 (AArch64)

Supports Linux and Darwin binaries. New in 1.5 and not as well exercised as other ports.

ppc64, ppc64le (64-bit PowerPC big- and little-endian)

Supports Linux binaries. New in 1.5 and not as well exercised as other ports.

mips, mipsle (32-bit MIPS big- and little-endian)

Supports Linux binaries. New in 1.8 and not as well exercised as other ports.

mips64, mips64le (64-bit MIPS big- and little-endian)

Supports Linux binaries. New in 1.6 and not as well exercised as other ports.

s390x (IBM System z)

Supports Linux binaries. New in 1.7 and not as well exercised as other ports.

Except for things like low-level operating system interface code, the run-time
support is the same in all ports and includes a mark-and-sweep garbage
collector, efficient array and string slicing, and support for efficient
goroutines, such as stacks that grow and shrink on demand.

The compilers can target the DragonFly BSD, FreeBSD, Linux, NetBSD, OpenBSD,
OS X (Darwin), Plan 9, Solaris and Windows operating systems.
The full set of supported combinations is listed in the discussion of
environment variables below.

See the main installation page for the overall system requirements.
The following additional constraints apply to systems that can be built only from source:

For Linux on PowerPC 64-bit, the minimum supported kernel version is 2.6.37, meaning that
Go does not support CentOS 6 on these systems.

Install Go compiler binaries

The Go toolchain is written in Go. To build it, you need a Go compiler installed.
The scripts that do the initial build of the tools look for an existing Go tool
chain in $GOROOT_BOOTSTRAP.
If unset, the default value of GOROOT_BOOTSTRAP
is $HOME/go1.4.

There are many options for the bootstrap toolchain.
After obtaining one, set GOROOT_BOOTSTRAP to the
directory containing the unpacked tree.
For example, $GOROOT_BOOTSTRAP/bin/go should be
the go command binary for the bootstrap toolchain.

To use a binary release as a bootstrap toolchain, see
the downloads page or use any other
packaged Go distribution.

To build a bootstrap toolchain from source, use
either the git branch release-branch.go1.4 or
go1.4-bootstrap-20171003.tar.gz,
which contains the Go 1.4 source code plus accumulated fixes
to keep the tools running on newer operating systems.
(Go 1.4 was the last distribution in which the toolchain was written in C.)
After unpacking the Go 1.4 source, cd to
the src subdirectory, set CGO_ENABLED=0 in
the environment, and run make.bash (or,
on Windows, make.bat).

To cross-compile a bootstrap toolchain from source, which is
necessary on systems Go 1.4 did not target (for
example, linux/ppc64le), install Go on a different system
and run bootstrap.bash.

When run as (for example)

$ GOOS=linux GOARCH=ppc64 ./bootstrap.bash

bootstrap.bash cross-compiles a toolchain for that GOOS/GOARCH
combination, leaving the resulting tree in ../../go-${GOOS}-${GOARCH}-bootstrap.
That tree can be copied to a machine of the given target type
and used as GOROOT_BOOTSTRAP to bootstrap a local build.

To use gccgo as the bootstrap toolchain, you need to arrange
for $GOROOT_BOOTSTRAP/bin/go to be the go tool that comes
as part of gccgo 5. For example on Ubuntu Vivid:

Install Git, if needed

To perform the next step you must have Git installed. (Check that you
have a git command before proceeding.)

If you do not have a working Git installation,
follow the instructions on the
Git downloads page.

(Optional) Install a C compiler

To build a Go installation
with cgo support, which permits Go
programs to import C libraries, a C compiler such as gcc
or clang must be installed first. Do this using whatever
installation method is standard on the system.

To build without cgo, set the environment variable
CGO_ENABLED=0 before running all.bash or
make.bash.

Fetch the repository

Go will install to a directory named go.
Change to the directory that will be its parent
and make sure the go directory does not exist.
Then clone the repository and check out the latest release tag
(go1.9, for example):

(Optional) Switch to the master branch

If you intend to modify the go source code, and
contribute your changes
to the project, then move your repository
off the release branch, and onto the master (development) branch.
Otherwise, skip this step.

where the details on the last few lines reflect the operating system,
architecture, and root directory used during the install.

For more information about ways to control the build, see the discussion of
environment variables below.
all.bash (or all.bat) runs important tests for Go,
which can take more time than simply building Go. If you do not want to run
the test suite use make.bash (or make.bat)
instead.

Note: The go command will install the godoc
binary to $GOROOT/bin (or $GOBIN) and the
cover and vet binaries to
$GOROOT/pkg/tool/$GOOS_$GOARCH.
You can access the latter commands with
"gotoolcover" and
"gotoolvet".

Community resources

The usual community resources such as
#go-nuts on the Freenode IRC server
and the
Go Nuts
mailing list have active developers that can help you with problems
with your installation or your development work.
For those who wish to keep up to date,
there is another mailing list, golang-checkins,
that receives a message summarizing each checkin to the Go repository.

Keeping up with releases

New releases are announced on the
golang-announce
mailing list.
Each announcement mentions the latest release tag, for instance,
go1.9.

To update an existing tree to the latest release, you can run:

$ cd go/src
$ git fetch
$ git checkout <tag>
$ ./all.bash

Where <tag> is the version string of the release.

Optional environment variables

The Go compilation environment can be customized by environment variables.
None is required by the build, but you may wish to set some
to override the defaults.

$GOROOT

The root of the Go tree, often $HOME/go1.X.
Its value is built into the tree when it is compiled, and
defaults to the parent of the directory where all.bash was run.
There is no need to set this unless you want to switch between multiple
local copies of the repository.

$GOROOT_FINAL

The value assumed by installed binaries and scripts when
$GOROOT is not set explicitly.
It defaults to the value of $GOROOT.
If you want to build the Go tree in one location
but move it elsewhere after the build, set
$GOROOT_FINAL to the eventual location.

$GOOS and $GOARCH

The name of the target operating system and compilation architecture.
These default to the values of $GOHOSTOS and
$GOHOSTARCH respectively (described below).

The name of the host operating system and compilation architecture.
These default to the local system's operating system and
architecture.

Valid choices are the same as for $GOOS and
$GOARCH, listed above.
The specified values must be compatible with the local system.
For example, you should not set $GOHOSTARCH to
arm on an x86 system.

$GOBIN

The location where Go binaries will be installed.
The default is $GOROOT/bin.
After installing, you will want to arrange to add this
directory to your $PATH, so you can use the tools.
If $GOBIN is set, the go command
installs all commands there.

$GO386 (for 386 only, default is auto-detected
if built on either 386 or amd64, 387 otherwise)

This controls the code generated by gc to use either the 387 floating-point unit
(set to 387) or SSE2 instructions (set to sse2) for
floating point computations.

GO386=387: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).

GO386=sse2: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.

$GOARM (for arm only; default is auto-detected if building
on the target processor, 6 if not)

This sets the ARM floating point co-processor architecture version the run-time
should target. If you are compiling on the target system, its value will be auto-detected.

GOARM=6: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)

GOARM=7: use VFPv3; usually Cortex-A cores

If in doubt, leave this variable unset, and adjust it if required
when you first run the Go executable.
The GoARM page
on the Go community wiki
contains further details regarding Go's ARM support.

$GOMIPS (for mips and mipsle only)

This sets whether to use floating point instructions.

GOMIPS=hardfloat: use floating point instructions (the default)

GOMIPS=softfloat: use soft floating point

Note that $GOARCH and $GOOS identify the
target environment, not the environment you are running on.
In effect, you are always cross-compiling.
By architecture, we mean the kind of binaries
that the target environment can run:
an x86-64 system running a 32-bit-only operating system
must set GOARCH to 386,
not amd64.

If you choose to override the defaults,
set these variables in your shell profile ($HOME/.bashrc,
$HOME/.profile, or equivalent). The settings might look
something like this:

export GOROOT=$HOME/go1.X
export GOARCH=amd64
export GOOS=linux

although, to reiterate, none of these variables needs to be set to build,
install, and develop the Go tree.